1. Field of the Invention
The present invention relates to a sensory structure of a touch panel, and more particularly to a sensory structure of a capacitive touch panel.
2. Description of the Related Art
Touch sensing technology is broadly applied in the present electronic application for data input. In this case, the information is read out or transmitted while the user touches the screen with the finger or the stylus, so that the buttons, keyboards or joysticks, which are desired for the conventional electronic apparatus, could be omitted.
Depending on the principles adopted for sensing, the touch panels are grouped into such as resistive touch panels, capacitive touch panels, infrared (IR) touch panels and ultrasonic wave ones. Regarding the IR touch panels and the ultrasonic wave ones, an IR or ultrasonic wave transmitting unit is arranged on one side of the respective X-direction and Y-direction of the screen, and on the other side thereof a receiving unit is configured. The movement of IR-ray or ultrasonic wave would be changed while the screen is touched by the user, and the touch position is accordingly measured and determined for data input. With respect to the resistive touch panel, which is fabricated by the lamination of an upper and a lower indium tin oxide (ITO) conductive films, the voltage variation thereof is generated while the upper and the lower electrodes of ITO are conducted through the touch pressure, and is detected by a controller, so that the touch position for data input is determined. The capacitive touch panel is constructed by the transparent glass substrate with a layer of metal oxide coated thereon, where a uniformly distributed electrical field is produced throughout the surface of the substrate by the application of voltage from the four corners thereof. By detecting the capacitance variation caused by static-electric reaction between the user's finger and the electric field, the touch position for data input is determined.
The capacitive touch panel is advantageous in the design of dust-preventing, anti-fire, anti-scratch and high resolution. Nevertheless, an erroneous determination may occur in case of being exposed to electrostatic or humid environment since the sensory structure of the capacitive touch panel is easily affected thereby. Accordingly, it is relatively more difficult to design the structure and circuitry of the sensory structure to further increase the sensitivity of the capacitive touch panel, and hence the fabrication cost thereof may be so significant.
U.S. Pat. No. 7,030,860 B1 discloses a capacitive sensing system with high transparency and sensitivity, in which the sensory structure is constructed with a flexible substrate and thus can be integrated into various kinds of electronic devices. With reference to FIG. 1A, the one-dimensional capacitive sensing system 1 according to U.S. Pat. No. 7,030,860 B1 is illustrated. The capacitive sensing system 1 is constructed by a transparent substrate 10 and a further transparent substrate 14 coated with a transparent conductive layer 16, where the substrates 10 and 14 are bonded with other by the application of an adhesive layer 12. Moreover, if a two-dimensional capacitive sensing system 100 is to be fabricated, a set of two different transparent substrates 14A and 14B must be provided on two opposite sides of an insulating layer 18 where the transparent substrates 14A and 14B have the respective transparent conductive layers 16A and 16B that are patterned in different directions, i.e. x-direction and y-direction respectively, as shown in FIG. 1B.
The above sensing system is designed as a multi-layer structure, so that the construction of the capacitive touch panel having the same is relatively complicated. Upon on fabrication, such sensing system needs five to ten film-processing procedures, and the use of two substrates as well as one to three full insulating layers is necessary, which fails to meet the demands for compactness. Furthermore, the above capacitive sensing system adopts the indium tin oxide (ITO) electrode for serving as the upper and lower conductive electrodes thereof, the sensitivity would be relatively reduced since the conductivity of ITO is insufficient for its high resistivity.
For overcoming the mentioned issues, it is desired in this art to provide a sensory structure of the capacitive touch panel with a relatively lower resistance so as to increase the sensitivity thereof. In addition, a sensory structure having a simplified structure and even reduced thickness is preferred for saving the fabrication cost thereof.